News Release Number: STScI-2004-13

Hubble Sees Stars as Numerous as Grains of Sand in Nearby Galaxy

April 8, 2004: What appear as individual grains of sand on a beach in the image
obtained with NASA's Hubble Space Telescope are actually myriads
of stars embedded deep in the heart of the nearby galaxy NGC 300.
The Hubble telescope's exquisite resolution enables it to see the
stars as individual points of light, despite the fact that the
galaxy is millions of light-years away.

Q & A: Understanding the Discovery

1.
Where is NGC 300 located?

NGC 300 is a spiral galaxy much like our own Milky Way galaxy. It is a
member of a nearby group of galaxies known as the Sculptor group, named
for the southern constellation where they can be found. The distance
to NGC 300 is 6.5 million light-years making it one of the Milky Way's
closer neighbors. At this distance the brightest individual stars can be
picked out even from ground-based images. With a resolution some 10 times
better than ground-based telescopes, Hubble's Advanced Camera for Surveys
ACS) resolves many more stars in this galaxy than have ever been seen before.

2.
How are astronomers using this image of NGC 300?

These Hubble data are being used to test a new method for measuring
distances to galaxies and to compare it with the more traditional
methods, such as the period-luminosity relationship of pulsating stars
known as Cepheid variables. Some of the luminous blue specks in this
image, young and massive stars called blue supergiants, are among the
brightest stars seen in spiral galaxies like NGC 300. By combining the
stellar brightness with other information, such as the stellar temperature,
surface gravity and mass outflow, astronomers are defining a new technique
to measure distances to galaxies located millions of light-years away.

3.
What do the different colors mean?

The color composite was made from filtered images taken in blue, green,
and infrared light. Hot, young blue stars appear in clusters that form
in the galaxy's spiral arms. Ribbons of deep red stars mark the location
of gauzy curtains of dust that partially hide the light of the stars
behind them. Near the center of the image is the bright and compact
nucleus of the galaxy where even the ACS loses the ability to separate
the densely packed stars.